OS: FreeBSD, CentOS, Windows family, ESXI;
Networking: Tcp/ip, iptables, routing, firewall, vpn, DNS;
Security: fail2ban;
Backup: Veeam backup;
Web: Apache, Nginx;
Monitoring: Nagios, The Dude;
Database: MySQL;
Version control: Svn;
Virtualization: VirtualBox, VMware Workstation, VMware vCenter and vSphere, VMware Horison;